The present invention relates to friction clutches in general, especially to friction clutches for use in motor vehicles or the like, and more particularly to improvements in clutch plates or clutch discs which can be used in friction clutches to transmit torque between the driving and driven components of the clutch. Still more particularly, the invention relates to improvements in clutch discs or clutch plates of the type wherein a first set of coil springs or analogous energy storing elements is interposed between the input and output elements of a primary damping unit and a second set of coil springs or analogous energy storing elements is interposed between the input and output elements of a secondary damping unit.
Clutch discs of the above outlined character are disclosed, for example, in German Utility Model No. 72 05 198. The clutch disc of this German Utility Model is constructed and assembled in such a way that the primary damping unit is effective within the entire range of angular movement of the driven component of the clutch with reference to the driving component and the second damping unit is effective during a certain stage of such angular movement, namely, following a stage during which the first damping unit constitutes the sole means for yieldably opposing rotation of the driven component relative to the driving component of the friction clutch or vice versa. Each of the two damping units comprises discrete input and output elements and discrete energy storing means interposed between the respective input and output elements and yieldably opposing rotation of the output elements relative to the respective input elements. The output element of the first damping unit can be provided with an internal profile which is complementary to the external profile of a shaft, e.g., the input member of a change-speed transmission in a motor vehicle, and each output element can further comprise a hub whereby the hub of the output element of the first damping unit extends into the hub of the output element of the second damping unit and has external teeth meshing, with circumferential clearance, with internal teeth of the hub which forms part of the output element of the second damping unit. The energy storing means of the first damping unit comprises a set of coil springs which are installed in registering windows of the input and output elements of the first damping unit, and the energy storing means of the second damping unit includes coil springs installed in registering windows of the input and output elements of the second damping unit.
A drawback of the just outlined conventional clutch plate is that it comprises a substantial number of parts and that its axial length is substantial; this contributes to the bulk and cost of the friction clutch wherein such clutch plate is put to use.